Fracture Characteristics of Austempered Spheroidal Graphite Aluminum Cast Irons

The fracture characteristics of austempered spheroidal graphite aluminum cast iron had been investigated. The chemical content of the alloy was C3.2, Al2.2, Ni0.8 and Mg0.05 (in mass percent, %). Impact test samples were produced from keel blocks cast in CO2 molding process. The oversized impact samples were austenitized at 850 and 950 degrees C for 2 h followed by austempering at 300 and 400 degrees C for 30, 60, 120 and 180 min. The austempered samples were machined and tested at room temperature. The impact strength values for those samples austempered at 400 degrees C varied between 90 and 110J. Lower bainitic structures showed impact strength values of 22 to 50J. The fractures of the samples were examined using SEM. The results showed that the upper bainitic fracture revealed a honey Comb-like topography, which confirmed the ductile fracture behavior. The lower bainitic fractures of those samples austempered for short times revealed brittle fracture

COMPARISON OF PROPERTIES OF TiN/TiCN AND PLASMA NITRIDING/TiCN FILMS DEPOSITED ON THE TOOL STEEL BY PULSED DC- PACVD

In this work, TiN/TiCN & PN/TiCN multilayer films were deposited by plasma- assisted chemical vapour deposition (PACVD). Plasma nitriding (PN) and TiN intermediate layer prior to coating leads to appropriate hardness gradient and it can greatly improve the mechanical properties of the coating. The composition, crystalline structure and phase of the films were investigated by X-ray diffraction. Atomic force microscopy and scanning electron microscopy were employed to observe the morphology and structure of the films. The TiCN layer exhibited a columnar structure. The adhesion force between the film and the tool steel substrate was 30.8 MPa for TiN/TiCN and 25.4 MPa for PN/TiCN film determined by pull off tests. The hardness of TiN/TiCN film was 12.75 GPa while it was 5.4 GPa for PN/TiCN film, respectively. The improvement of the adhesion in TiN/TiCN was attributed to a less gradient hardness configuration. In addition, the mean friction coefficients of the films were about 0.2 for TiN/TiCN and 0.3 for PN/TiCN film determined by nanoindentation tests

Effect of tool transverse speed and pin offset on the properties of friction stir welding Al6061-St52 dissimilar joint

The present study aimed to create an Al6061-St52 dissimilar joint and investigate the effect of the transverse speed and the pin offset by the friction stir welding (FSW) process. Aluminum to steel dissimilar welding is difficult by fusion methods because of the formation of brittle intermetallic compounds (IMCs). Therefore, FSW parameters were determined to designate optimal IMC thickness and acceptable mechanical properties. This research was carried out at different transverse speeds of 16, 25, 40, 55, 70, and 85 mm/min (with a constant pin offset of 0.2 mm), and various offsets of 0.8 mm, 0.4 mm, and 0 mm (with a constant transverse speed of 85 mm/ min). During the study of the transverse speed parameter, the highest ultimate tensile strength (UTS) of 200 MPa was obtained at 85 mm/min, while during the investigation of the offset parameter, the highest UTS of 175 MPa was achieved in the offset of 0.4 mm. According to the Energy Dispersive X-ray Spectroscopy results, an IMC layer formed in the joint interface. The heat input rate was calculated to designate the optimal parameters. In tensile specimens, fracture mainly occurred in the joints and within the aluminum stir zone due to the combination of thick IMC layer and steel fragments, respectively. Because of the presence of different microstructures, various hardness values were observed in the weld zone. The micro-hardness measurement showed that at the transverse speed of 85 mm/min the hardness values were 75 HV in the aluminum stir zone and 315 HV in the AS vicinity of the interface region. This hardness value was much higher than the base metals (Aluminum base metal is an average of 53 HV and an average steel base metal of 245 HV)

DISLOCATIONS STRUCTURE AND SCATTERING PHENOMENON IN CRYSTALLINE CELL SIZE OF 2024 AL ALLOY DEFORMED BY ONE PASS OF ECAP AT ROOM TEMPERATURE

Variation in microstructural features of 2024 aluminum alloy plastically deformed by equal channel angular pressing (ECAP) at room temperature, was investigated by X-Ray diffraction in this work. These include dislocation density dislocation characteristic and the cell size of crystalline domains. Dislocations contrast factor was calculated using elastic constants of the alloy such as C 11, C 22 and C 44 . The effect of dislocations contrast factor on the anisotropic strain broadening of diffraction profiles was considered for measuring the microstructural features on the base of the modified Williamson-Hall and Warren-Averbach methods. Results showed that the dislocations density of the solution annealed sample increased from 4.28×10 12m-2 to 2.41×10 14m-2 after one pass of cold ECAP and the fraction of edge dislocations in the solution annealed sample increased from 43% to 74% after deformation. This means that deformation changed the overall dislocations characteristic more to edge dislocations. Also the crystalline cell size of the solution annealed sample decreased from 0.83μm to about 210nm after one pass of ECAP process at room temperatur

Influence of citicoline on citalopram-induced antidepressant activity in depressive-like symptoms in male mice

Depression is associated with significant functional disabilities. Application of new drugs which could enhance the effectiveness of antidepressants drug and reduce side effects of their long-term use seems necessary. Citicoline is used as an effective chemical agent for improving the symptoms of some neurodegenerative diseases. Therefore, in this survey, the application of citicoline as an adjuvant drug was evaluated in mice model of depression. A total of 180 adult NMRI male albino mice were used in this study. All groups were exposed to chronic unexpected mild stress (CUMS) followed by treatment with various doses of citalopram or/and citicoline or saline for 21 days. Sucrose preference (SP), open field (OF), and forced swimming test (FST) were applied to evaluate depression symptoms in the groups. The results indicated that only citicoline at the 5 mg/kg dose had shifted its status from being noneffective to become significantly effective in the co-administered group. The means of SP, OFT, and FST of the treatment groups were significantly different in favor of co-administered group compared with the other groups as well as the control group. Based on the results, it can be concluded that administration of citicoline, as an adjuvant drug, in combination with citalopram, enhanced the effectiveness of selective serotonin reuptake inhibitors (SSRI) drugs for depression treatment. © 201